This invention relates to a self-contained stump grinding apparatus with a rotating disc cutter for mounting on hydraulic excavator lift arms so that the cutting face of the disc cutter is in the line of sight of the operator and the weight of the engine is utilized to stabilize the grinding movement.
A stump grinding apparatus with a quick connection to an excavator for moving the stump grinder to a position adjacent a stump and with the cutter head being moveable independently of the excavator boom is shown in U.S. Pat. No. 6,021,825. However, there is no provision for utilizing the excavator boom to control the cutting operation. In addition, the combined weight of the stump grinding apparatus is not utilized to absorb vibration and stabilize the grinder during the stump grinding operation.
A self contained tree stump grinder as shown in U.S. Pat. No. 5,419,380 includes a sled supported grinder which is placed by a backhoe excavator boom at a position adjacent a tree stump and dragged over the stump towards the backhoe during the grinding operation. The stump is between the operator and the cutter until the cutter reaches the edge of the stump at which time the debris is directed toward a guard between the operator and the cutter. The operator therefore does not know how effective the cutter is until it is lifted off the stump which makes it difficult to pull the cutter over the stump at an optimum speed. The grinder cannot grind stumps over the width of the grinding drum located between the sled runners and the grinding depth is limited by the height of the runners.
The grinding of stumps with a rotating disc cutter on the end of lift arms of a vehicle is shown in U.S. Pat. No. 3,818,957. The disc cutter is mounted on a boom close to the vehicle so that it can be tilted to maintain the position of the disc cutter facing the ground and with the operator shielded from the debris by the vehicle. One of the difficulties is that the operator cannot observe the cutting action without backing the vehicle away from the cut area. Also the debris is directed towards the vehicle unless multiple discs are used and a chute is provided to collect the chips and deposit them alongside the vehicle in a windrow. Two cutting wheels are proposed to grind up brush landing on top the generally horizontal disc.
The present invention is directed to a self-contained stump grinder attachment to a stick lift arm of a hydraulic excavator or other construction and forestry machines and to a method of grinding stumps where the operator can observe the grinding operation with a minimum risk of flying debris. By incorporating a rotating disc cutter with cutting teeth on one face, the full face of the disc can be utilized to cut through a tree stump. Also the disc cutter has a diameter greater than the width of the other parts of the self-contained grinder so that the disc will cut a path completely through the stump which results in a minimum of passes. The cutter engine driving the disc cutter is mounted in the same manner as an excavator bucket is mounted and is operated in a similar manner reducing the training time for an operator. During operation, the cutting face of the disc cutter is in the line of sight of the operator because the disc is rotated about an axis close to the line of sight and the debris is directed away from the axis. Also, the weight of the cutter engine stabilizes the movement of the cutter during the grinding operation. With wireless controls of the engine in the self-contained unit and use of a quick coupler unit, the stump grinder of the invention may be picked up and be in operation without the operator leaving the excavator.
It is understood that the cutter engine may be an electric motor or a hydraulic motor where there is a source of adequate hydraulic or electric power.
In accordance with one aspect of the invention there is provided a method of grinding a tree stump with a rotating disc cutter on a rotatable shaft of a power unit mounted on a grinder frame supported by lift arms of an excavator where an operator is located on the excavator characterized by moving the left arms to locate the rotating disc cutter at a position on the opposite side of the tree stump from the excavator, tilting the frame to incline the shaft toward the excavator so that a cutting face of the rotating cutter disc is in the line of sight of the operator on the excavator, moving the rotating disc cutter toward the excavator in cutting engagement with the stump and advancing the rotating disc cutter through the stump so that debris is discharged radially to one side and away from the operator.
In accordance with another aspect of the invention there is provided a stump grinding apparatus comprising a power unit having a rotatable disc cutter mounted on a first lift arm, the first lift arm being pivotally mounted on a second lift arm, the second lift arm being pivotally mounted on an excavator platform, the platform being rotatable about a generally vertical axis, first power means for lifting and lowering of the first lift arm, second power means for lifting and lowering of the second lift arm to provide curling movement of the power unit and the cutter disc toward and away from the platform and maintain an axis of rotation of the disc cutter inclined in a direction toward the excavator platform whereby debris from cutting rotation of the disc cutter will be discharged in a direction away from the platform.